Memory device



F. R. BRADLEY, JR 3,392,375

MEMORY DEVICE Filed April 21. 1964 '5 68 676 65 3 I M 59 INVENTOR.

JCPIMA/ e 54DAXJ2 6/ 57 BY zrraen/ars United States Patent 3,392,375 MEMORY DEVICE Frank R. Bradley, Jr., 9 Dash Place, Riverdale, N.Y. 10471 Filed Apr. 21, 1964, Ser. No. 361,525 Claims. (Cl. 340173) ABSTRACT OF THE DISCLOSURE This invention relates to the art of memory devices, more particularly of the type employing a magnetically variable electrical signal generator in the form of a variable resistor whose resistance varies with variations in the value of the magnetic field applied thereto, said resistor being set to a value to provide an electrical signal that is of value related to the value of an input signal.

As conducive to an understanding of the invention, it is noted that certain electrical signal generators have properties such that with changes in the magnetic field associated therewith, the output signal will change accordingly.

Thus, for example, certain materials such as indium antimonide provide a resistance whose value varies with variations in the strength of a magnetic field associated therewith.

More particularly, as shown in co-pending application Ser. No. 199,463, filed June 1, 1962, now Patent No. 3,131,381, an electrical signal generator such as a Hall Plate is used as a memory device to remember a given input signal said electrical signal generator having a permanent magnet associated therewith and there is associated with the magnet a coil through which flows a current that is generated by the difference between the signal to be remembered and the output of the electrical signal generator.

The flux or magnetism of the permanent magnet will change due to the current through the coil and consequently the electrical signal generator output will change until it is equal to the value of the signal to be remembered at which time since the signals through the coil are equal and in opposition there will be no more current flow through the coil. Thus, the permanent magnet will have a set flux or magnetism so that if the signal to be remembered is then removed, the signal from the electrical signal generator will be equal to the signal to be remembered.

The device is useful therefore in many applications such as to store information in computors until the information is required for various mathematical computations.

The device, according to said copending application Ser. No. 199,463, was only capable of providing a voltage output and in some applications it is desired to have not only a current output, but a voltage output or a resistive output.

It is accordingly among the objects of the present invention to provide a memory device that utilizes a magnetically variable resistor in place of a Hall Plate and in which the remembered signal may be read out as a resistance, a current or a voltage.

According to the invention, these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claims.

In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention,

FIG. 1 is a circuit diagram of one embodiment of the invention in which the input signal is a resistance of value proportional to the signal to be remembered,

FIG. 2 is a diagrammatic view illustrating the use of the embodiment of FIG. 1 to provide a voltage output,

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FIG. 3 is a view similar to FIG. 2 illustrating the use of the embodiment of FIG. 1 to provide a current output,

FIG. 4 is a circuit diagram of another embodiment of the invention in which the input signal is a voltage of value proportional to the signal to be remembered, and

FIG. 5 is a circuit diagram of still another embodiment in which the input signal is a current of value proportional to the signal to be remembered.

Referring now to the drawings, in the embodiment shown in FIG. 1, the electrical signal generator comprises a magnetically variable resistor 11, one of the ends of which is connected to a terminal 12, the other end of the resistor 11 being connected to the contact arm 13 of a switch 14 and adapted to engage either fixed contact 15 connected to terminal 16 of a Wheatstone bridge circuit 17 or fixed contact 18 connected to output terminal 19. The terminal 12 which is connected to output terminal 21 is also connected to input terminal 22 which has associated therewith a second input terminal 23, the signal to be remembered which would be in the form of a resistance R of value proportional to the signal to be remembered being applied across said terminals 22 and 23. The terminal 23 is connected to terminal 24 of said bridge and said terminals 16 and 24 are connected to the respective ends of a coil 25 wound around a leg 26 of a permanent magnet 27 between the poles 28 and 29 of which the magnetically variable resistor 11 is positioned. To complete the bridge circuit, the terminals 16 and 24 are connected through fixed resistors 31, 32 which illustratively are equal in value to a terminal 33 and a source of potential which may be supplied by a battery 34, is connected across terminals 12 and 33.

In operation of the equipment shown in FIG. 1, a resistance R of value proportional to the signal to be remembered is applied across terminals 22 and 23 thereby forming the unknown arm of the bridge circuit and completing such bridge circuit. Assuming that resistors 31 and 32 are equal in value, and the resistor R applied across terminals 22 and 23, dilfers in value from resistor 11, the bridge 17 will be unbalanced and current will flow through the coil 25 connected across terminals 16 and 24.

As a result of such current flow through coil 25, the flux level of said magnet 27 will change thereby changing the resistance value of magnetically variable resistor 11 until said resistor 11 is equal to the value of resistor R applied across terminals 22, 23 at which time no further current will flow through the coil 25.

At this time the contact arm 13 of the switch 14 may be moved to engage contact 18 and consequently, the re sistor 11 alone will be in circuit in series with terminals 19 and 21 and due to the existing flux level of magnet 27 said resistance will have a value equal to the value of resistance R across terminals 22, 23.

It is to be noted that the direction of the current through coil 25 will be dependent upon which of resistors 11 and R has the greater value and the flux of the magnet 27 will either be increased or decreased depending upon the direction of such current flow.

The circuit shown in FIG. 1 may be readily utilized to provide an output of resistance, voltage or current. Thus, the circuit shown in FIG. 1 furnishes a resistance value that is proportional to the value of the resistance applied across terminals 22 and 23, i.e., the value of resistor 11 as set forth in the manner above described.

The resistor 11 can be utilized to provide a voltage or current output as shown in FIGS. 2 and 3 respectively. Thus, as shown in FIG. 2, the resistor 11 is switchedso that it is in series with a constant current source 41 and a voltmeter 42 having a high impedance with respect to the value of resistor 11, is connected in parallel with such resistor 11 so that it will indicate the voltage through said resistor 11 effected by the constant current source 41.

In the embodiment of FIG. 3, the resistor 11 is switched into a series circuit containing a constant voltage source 43 and an ammeter 44 having a low resistance with respect to the resistor 11 and such ammeter will give an indication of the current flowing through said resistor 11 depending upon the value of the latter.

The equipment above described and shown in FIGS. 1 to 3 inclusive, thus permits a signal to be remembered that is in the form of a resistance R of value proportion to such signal to be read out as either a resistance, a current or a voltage.

In the embodiment shown in FIG. 4, the signal to be remembered is in the form of a voltage V of value proportional to such signal. Thus, referring to FIG. 4, the magnetically variable resistor 11' is positioned between the poles of a permanent magnet 27' and a coil 25' is wound around the leg 26' of the magnet. One end of the resistor 11' is connected to a terminal 45 and the other end to a terminal 46. One end of the coil 25 is connected to the terminal 46 and the other end is connected to terminal 47, said terminals 45 and 47 defining the input to which the signal to be remembered in the form of a voltage V is applied.

Connected across terminals 45, 46 is a constant current source 48 and the output terminals 49 and 51 which are connected to a load that is of high impedance with respect to the value of resistor 11 are connected to terminals 46 and 45 respectively.

In the operation of the equipment shown in FIG. 4 the current from constant current source 48 flowing through magnetically variable resistor 11' develops a voltage across said resistor 11.

If the voltage applied to opposite sides of the coil 25' resulting from the signal V to be remembered and the voltage developed across the resistance 11' by the constant current source 48 are of equal polarity and of equal value there will be no current flow through the coil 25 and hence the flux level of permanent magnet 27 will remain unchanged and the resistance 11' will have a set value based on the flux of the magnet. If one of the voltages is greater than the other, then current will flow through the coil 25' in the direction of such difference of value thereby increasing or decreasing the magnitude of the flux of the magnet and consequently changing the value of resistor 11.

Since the output terminals 49, 51 are across the resistor 11' and since the load applied across the output terminals is of very high impedance with respect to the value of resistance 11', a voltage will be developed across the load connected across the output terminals which is of value equal to the value of the voltage to be remembered.

The embodiment shown in FIG. is designed to provide an output current that is proportional to the value of an input current, such input current being proportional to the vale of the signal to be remembered. In the embodiment shown in FIG. 5, the magnetically variable resistor 11" is positioned between the poles of the magnet 27". One end of the resistor 11" is connected to terminal 55 connected to one side of a constant voltage source 56 and the other side of said constant voltage source 56 is connected to the contact arm 57 of a switch 58. The switch 58 has a second contact arm 59 to which the other end of resistor 11" is connected and a third contact arm 61 ganged with the other contact arms and which is connected to input terminal 62. The switch has three pairs of fixed contacts 63, 64, 65, 66 and 67, 68, associated with contact arms 59, 57 and 61. The contact arm 59 normally engages fixed contact 63 which is connected to one end of coil 71 wound around leg 72 of the magnet 11", the other end of said coil 71 being connected to fixed contact 65 engaged by contact arm 57. The fixed contact 67 is connected to one end of a coil 73 also wound around the leg 72 of the magnet 11" and the other end of said coil 73 is connected to input terminal 74. The fixed contacts 64 and 66 are connected to a low impedance load which may be an ammeter 75, for example.

In the operation of the equipment shown in FIG. 5, when a current is applied to the input terminals 62, 74 of value proportional to that of the signal to be remembered, it will cause a magnetic field to be developed by coil 73. At the same time, due to the constant voltage source 56 in series with resistor 11" and coil 71, a magnetic field will also be developed by said coil 71. The coils 71 and 73 are connected so that the magnetic fields created thereby are in opposition and consequently when said magnetic fields are equal, there will be no further magnetic field created. This will occur when the resistance 11" is of value such that the current flowing through coil 71 is equal and opposite to that flowing through coil 73, assuming that the coils are of identical configuration.

At this time, the switch 58 may be actuated to connect contact arms 59 and 57 to fixed contacts 64 and 66 and this will therefore connect the low impedance load or ammeter 75 in series with the resistor 11 and constant voltage source 56. Since the resistor will have been set to a value proportional to that of the signal to be remembered by reason of the flux level of magnet 27", the ammeter will therefore show a current indication also proportional to that of the signal to be remembered.

The equipments above described thus provide a highly eflicient means for memorizing an input signal that may be in the form of resistance, voltage or current and providing an output signal in similar form.

As many changes could be made in the above equipments, and many apparently widely different embodiments of this invention could be made Without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A device for remembering an input signal comprising a magnetically variable resistor whose resistance varies with variations in the magnetic field applied thereto, means to provide current flow through said resistor, a permanent magnet associated with said resistor for creating a magnetic field, a coil wound around said magnet to modify such magnetic field, a bridge circuit having four arms, said magnetically variable resistor being connected into one arm of said bridge, means to connect a resistor of value related to the value of the signal to be remembered into a second arm of said bridge, two additional resistors connected respectively into the third and fourth arms of said bridge, said coil being connected across two opposed junctions of said bridge, the means to provide current flow through said resistor being connected across the other two opposed junctions of said bridge, to provide a current output from said magnetically variable resistor in direction to oppose the current through said resistor of value related to the value of the signal to be remembered, whereby when said two currents are in balance, the resistance value of said magnetically variable resistor will be equal to the value of the resistor related to the value of the signal to be remembered, a constant current source, means to switch said magnetically variable resistor from said bridge circuit into series with said constant current source, and a high impedance load connected in parallel with said magnetically variable resistor.

2. A device for remembering an input signal comprising a magnetically variable resistor whose resistance varies with variations in the magnetic field applied thereto, means to provide current flow through said resistor, a permanent magnet associated with said resistor for creating a magnetic field, a coil wound around said magnet to modify such magnetic field, a bridge circuit having four arms, said magnetically variable resistor being connected into one arm of said bridge, means to connect a resistor of value related to the value of the signal to be remembered into a second arm of said bridge, two additional resistors connected respectively into the third and fourth arms of said bridge, said coil being connected across two opposed junctions of said bridge, the means to provide circuit flow through said resistor being connected across the other two opposed junctions of said bridge, to provide a current output from said magnetically variable resistor in direction to oppose the current through said resistor of value related to the value of the signal to be remembered, whereby when said two currents are in balance, the resistance value of said magnetically variable resistor will be equal to the value of the resistor related to the value of the signal to be remembered, a constant voltage source, means to switch said resistor from said bridge circuit into series with said constant voltage source, and a low impedance load connected in series with said series connected resistor and constant voltage source.

3. A device for remembering an input signal comprising a magnetically variable resistor whose resistance varies with variations in the magnetic field applied thereto, a constant voltage source to provide current flow through said resistor, a permanent magnet associated with said resistor for creating a magnetic field, a coil wound around said magnet to modify such magnetic field, one end of said coil being connected to one end of said resistor, and the other end of said coil being connected to an input terminal, a second input terminal connected to the other end of said resistor, said two input terminals providing means to apply a voltage signal to said magnetizing means, and means to apply the current output of said resistor to said magnetizing means in direction to oppose the input signal, whereby when said input and output signals are in balance, the resistance value of said resistor will correspond to the value of the input signal.

4. A device for remembering an input signal comprising a magnetically variable resistor whose resistance varies with variations in the magnetic field applied thereto, a constant voltage source to provide current flow through said resistor, a permanent magnet associated with said resistor for creating a magnetic field, a pair of coils wound around said magnet to modify such magnetic field, a pair of input terminals connected to the ends of one of said coils to apply an input current signal thereto, one side of the constant voltage source being connected to one end of said resistor and the other side of said constant voltage source being connected to one end of the other coil, the other end of said other coil being connected to the other end of said resistor, whereby said resistor, said other coil and said constant voltage source are connected in series with the current through said resistor applied in direction to oppose the input current so that the value of the resistor will be such as to provide a current equal to the input signal current.

5. The combination set forth in claim 4 in which means are provided to break the circuit from said input terminals to said first coil and to switch said series connected resistor and constant voltage source from said second coil to a low impedance load.

References Cited UNITED STATES PATENTS 2,894,234 7/1959 Weiss 338-32 TERRELL W. FEARS, Primary Examiner. 

